Abstract: The diamond coating was prepared on the surface of the cemented carbide step cutting tool by using double-layered hot filament assisted chemical vapor deposition (CVD). Then the drilling characteristics and wear properties of the uncoated and coated cutting tools during drilling the composite fiber brake pad, as well as the surface qualities of the machined hole, were compared and analyzed. The results show that under the high speed drilling condition, the axial force and torque of coated cutting tool were obviously lower than those of uncoated cutting tool, showing a better drilling performance. After drilling 10 holes at the same speed and feed rate, the flank wear height of the coated cutting tool was about 0.025 mm, which was much less than the wear standard (0.2 mm), while that (0.15 mm) of uncoated cutting tool was close to the wear standard, indicating that the wear resistant of the coated cutting tool was better than that of uncoated cutting tool. The hole boundary drilled by the coated cutting tool was smooth and had no burr and tearing. The surface quality was better than that drilled by uncoated cutting tool.